| Competition: | Irish League |
| Season: | 1990–91 |
| Winners: | Portadown 2nd Irish title |
| Matches: | 240 |
| Total Goals: | 748 |
| League Topscorer: | Stephen McBride (22) |
| Prevseason: | 1989–90 |
| Nextseason: | 1991–92 |
The 1990–91 Irish League was the 90th edition of the Irish League, the highest level of league competition in Northern Irish football.
The league consisted of 16 teams, an increase from the previous season of 14 as Ballyclare Comrades and Omagh Town joined. Portadown won the championship.